In 1940, he joined the Royal Australian Naval Volunteer Reserve (RANVR) for service in World War II.

Quickly sent back to the United Kingdom, he served on several shore establishments before being sent to British India as a naval mine clearance specialist.

He returned to the UK in late 1944, and in April 1945 he was given command of a naval party responsible for mine clearance in the recently captured Bremen Harbour in Germany.

He displayed exceptional courage in defusing three mines under very difficult conditions between 8 and 19 May 1945, which resulted in him being awarded the George Cross.

Gosse continued to serve in the RANVR after the war, reaching the rank of lieutenant commander before retiring in 1958, and died of a heart condition in 1964.

Gosse then worked at odd jobs for a few years, and on 1 October 1938 he married Diana Skottowe at his old school chapel.

[1] Transferred back to the UK in November 1944,[2] Gosse was posted to the shore establishment HMS Vernon at Brixham, Devon, which was the European port clearance diving base for the Royal Navy.

[8] According to his entry in the Australian Dictionary of Biography, he was a bit of a "law unto himself" in this period,[1] but was fascinated with mechanical devices and exhibited inventiveness.

[1] Following the capture of Bremen, Germany, in April, Gosse led Naval Party 1571 to the port to clear mines laid by the retreating Germans in the Überseehafen.

[1][9] Prior to being sent forward to Bremen, Gosse had interrogated a German prisoner of war (POW) who had been involved in the demolition of the Überseehafen and its facilities who described a mine known as an "Oyster", which was "impossible to sweep for and could never be rendered safe".

[4] Another officer from Naval Party 1571 said later that "if Gosse hadn't found an answer to the ["Oyster"], Bremen Harbour would have been unusable".

The citation read:[13] On the 8th May, 1945, divers searching Ubersee Hafen reported the presence of a mine which from their description appeared to be an entirely new type.

[14] Three days after his GC was promulgated, Gosse was visited at home by a journalist from The Advertiser daily newspaper and was surprised to learn he was to receive an award for doing something he enjoyed so much.

[15] Gosse was invested with his George Cross in Adelaide on 3 June 1948 by the Governor of South Australia, Lieutenant General Sir Willoughby Norrie.

[1] During 1950, Gosse was part of an Australian armed forces recruiting campaign throughout South Australia, before collapsing from nervous strain at a rally in Renmark.

[1] The Victoria Cross recipient Brigadier Sir John George Smyth wrote that Gosse "always lived right on top of the world, as though every day was his last".